A drill tool connected to a drilling machine by means of one or more drill string components is often used at rock drilling. The drilling may be performed in a number of ways, e.g., as rotational drilling, wherein the drill tool is pushed towards the rock using high pressure and then crushes the rock using hard metal elements, e.g., made from wolfram carbide. Another way of performing rock drilling is to use percussive drilling machines, wherein the drill string is provided with a drill steel shank at which a piston impacts to transfer impact pulses to the drill tool through the drill string and then further onto the rock. Percussive drilling is combined with a rotation of the drill string in order to achieve a drilling wherein the drill elements of the drill bit hits new rock at each impact, (e.g., does not hit a hole generated by the previous impact), which increases drilling efficiency.
A problem using rotational drilling is that in certain conditions, the drill bit (the drill bit elements of the drill bit) may “get stuck” in the rock, whereby the rotation of the drill bit stops at the same time as the drill string continues to rotate due to system inertia. This results in a torsion oscillation in the drill string, which, in turn, is the source of a loosening (releasing) force, which tends to loosen (release) joints of the drill tool and/or drill string and or drilling machine, as these joints usually consist of threaded joints which may unthread by the loosening force. This loosening of joints causes damaging heat generation and damages threads.